Dental casting machine



June 23, 1942p H,|,BE ER 2,287,508

DENTAL CASTING MACH INE F iled May 3, 1941 2 Shets -Sheet 1 June 23, 1942. H. R. BERGER 2,287,503

' DENTAL CASTING MACHINE M. Filed' May 3. 1941 "sl i ts -sheet 2 @l/II/IIIIIIZ i Herbert lflfierger Patented June 23, 1942 DENTAL CASTING MACHINE Herbert R. Berger, Brooklyn, N. Y., assignor to J. F. Jelenko & Co. Inc., New York, N. Y., a corporation of New York Original application September 28, 1938, Serial Divided and this application May 3, 1941, Serial No. 391,685

6 Claims. Y (Cl. 22- 65.1)

The present invention relates to improvements in casting apparatus of the type'capable of use in dental and jewelry work, or similar work, and this application is a division of my application Serial No, 232,207, filed September 28, 1938, now Patent No. 2,245,065.

In the casting of metals for dental work, jewelry, and other fine work by the usual centrifugal methods in which visual inspection is relied upon to determine the proper time for molding, many defects are often present in the finished castings. An important object of the present invention is the provision of a casting apparatus which will be free from the disadvantages of the prior art and which will produce castings of a uniform-character and good quality.

A further object of the invention is to provide a casting apparatus of simple and inexpen sive construction, capable of electrical melting of the metal in a simple and readily controlled manner.

Another object of the invention is the provision of an apparatus of this character which may be manufactured as a complete unit or as an attachment to be applied to centrifugal machines now in use.

Other objects and advantages of the invention will be apparent during the course of the following description.

In the accompanying drawings, which form a part of this specification and wherein like characters of reference denote like parts throughout,

Figure 1 is an elevation of a casting apparatus embodying the present invention and of the type capable of use with centrifugal apparatus now in use,

Figure 2 is a top plan view thereof,

Figure 3 is a vertical sectional view taken on the line 33 of Figure 1,

Figure 4 is a front elevation of the electrical v ,In the drawings, wherein for the purpose of illustration is shown a preferred embodiment of the invention, the numeral l designates the base of a centrifugal casting machine of the type now in use in which a central vertical shaft II projects above the casing and is connected to a spring motor or other source of power within the casing which is adapted to rotate the shaft H at high speed. Casings and shafts of this type are in common use with various types of centrifugal casting machines. A horizontal bar 12 is removably secured to the upper end of shaft I l to rotate therewith.

A furnace or oven I3 is rigidly secured to the bar l2 by means of a pair of clamping members l4 removably bolted at IE to the bar I2 at a point between the shaft II and one end of the bar I2. The furnace is supported above the bar,

"and when it is desired to remove the furnace,

bolts l5 are removed and the furnace and clamp slid from the bar longitudinally thereof. In order to insure proper location of the furnace, bolts I5 extend through suitable openings in the bar.,

The upper ends of .clamp members M are removably secured to the outer casing of the furnace by means of bolts I6. Clamp members M are provided with a pair of arms I! which ex-- tend below bar l2 one on. each side thereof. A panel or contact block I8 is removably secured between arms I! by means of suitable bolts 19.

The furnace or oven l3 has an outer metal casing 2|] which is cylindrical in shape and closed by end Walls 2|. A cylindrical refractory muflle 22 is embedded in the end walls of the furnace 'and is spaced a substantial distance from the asbestos fiber or other suitable heat insulatin material 24'. The insulating material 24' fills the space between the windings'23 and the casing 20.

A thermocouple 25 is disposed in the muflle 22 and is connected by suitable wiring to the two upper contacts 26 on contact block IS. The two lower contacts 21 are connected by suitable wiring to the resistance elements 23. The contacts 26 and 21 are disposed in a vertical row adjacent the inner edge of contact block I8,-

projecting a short distance laterally beyond the panel or contact block.

A sliding contact holder comprises a bifurcated holder block 28 removably secured to the top of casing H! by means of lateral brackets 29. detachably bolted to the casingtop. The lower portion of holder block 28 is shaped to conform to the top of the casing and is secured to brackets 29 by means of suitable bolts 30. A slidin contact plate 3| is slidably disposed in the bifurcated portion of the holder block and may be moved outwardly against the tension of a coil spring 32 by means of a finger piece or lug 33 extending through an elongated horizontal slot in the holder block. A cover cap 34 closes the top of block 28 while horizontal spring metal contact strips 35 are bolted to the inner end of the plate 3|. The contact strips 35 are spaced to engage the contacts 26 and 21. A flexible cable 36 carries wires connected to the contact strips 35 and terminates in a pronged plug 31, the prongs of which vary in diameter to insure the proper electrical connections for the winding 23 and thermocouple 25.

The contact carrying plate 3| is usually in the retracted position indicated in Figures 1 and 6. When the bar i2 is revolved to wind up the spring in casing I0, plate 3| is moved outwardly against the tension of spring 32 to place contact strips 35 inthe path of contact block I 8 and contacts 26 and 21. The pressure of bar l2 and the casing spring will hold the plate 3| in extended position and prevent rotation of bar l2. When it is desired to release bar 2 for rotation, it is moved away from plate 3| against the tension of the casing spring, allowing spring 32 to retract plate 3|. Bar l2 may then be released to rotate with shaft II. It will be seen that holder block 28 and sliding contact plate 3| may be readily attached to bases now in use, by means of the bolts on brackets 29.

By reference to Figure 6 it will be seen that the front end of the furnace casing is provided with a circular opening 38 which coincides with the inner periphery of the muffle 22. A smaller opening 39 is disposed in the rear wall of the furnace casing in concentric relation with the muflle. A door 40 fits in opening 38 and is pivoted at 4| adjacent the top of the furnace casing. A transparent window 42 may be arranged in the center of the door 40.

22 and has a sprue 44 which extends through the opening 39 to the gate of the mold 45. The crucible 43 and door 40 are held in place by centrifugal force when the bar I2 is rotated. The inner walls of the crucible taper at their ends to the opening in sprue 44. The end of the crucible opposite the sprue has an opening 46 therein of substantially less width than the inner periphery of the crucible and concentric therewith. A slot 41 is preferably arranged in the top of the crucible to register with the thermocouple 25.

A flask holder 48 is frusto-conical in shape and has a depending leg provided with a slot 49 to slidably receive the bar l2. A removable pin 50 in the end of the bar l2 normally prevents removal of the holder 48. A flask or mold 45 is arranged between the furnace 20 and the frusto-conical portion of the holder 48. A cradle 51 is provided with a pair of depending legs 52 adapted to straddle the bar I2, and supports mold 45 in position to be engaged by flask holder 48. The cradle may be lifted vertically from bar I2 for removal, and may be adjusted longitudinally along the bar. Various size cradles are provided to accommodate different molds.

A clamping bolt 53 extends through the bottom of flask holder 48 into slot 49 and is provided with a handle 54 for easy operation. In

operation, mold 45 is placed in cradle 5| in engagement with sprue 44, and flask holder 48 is moved into clamping engagement therewith. Bolt 53 is then tightened to lock holder 48 on bar [2. The frusto-conical shape of the holder 48 assures proper centering of the mold 45. In order to produce a clamping action on the mold when bolt 53 is tightened, slot 49 is disposed at a slight angle to a horizontal plane, as indicated in Figure 6, so that tightening of bolt 53 will tilt the holder and move the top of holder 48 towards the furnace 20 and firmly clamp the mold, as seen in Figure 1.

A cylindrical counterweight 55 is provided with a longitudinal slot to slidably receive the bar l2 on the side of shaft opposite the furnace. A plate 56 is bolted to the lower side of the weight 55 to close the bottom of the slot therein. A handle member 51 extends above the weight 55 and has a reduced removable shank 58 extending through a vertical bore into the slot. The lower end or head of shank 58 is adapted to be re-' ceived in one of a series of spaced openings 6|! in the top of bar |2. A coil spring 59 surrounds the shank within the weight slot and engages the head of the shank to normally force the shank into the openings 60. When it is desired to change the position of weight 55, shank 58 is released from openings 60 by raising handle 51 against tension of spring 59. The weight handle 51 is also used to rotate the bar I2 and shaft II, as when winding up the spring motor in casing I0. A removable, supplementary weight 6| has a slot to receive the bar l2 and a horizontal pin 62 adapted to extend into and opening in weight 55 to interlock the two weights. Pins 63 on bar |2 limit movement of the weights 6| and 55 and may be detachably secured to the bar.

In Figures 1 to 6, the arm I2 is shown as attached to the usual base III. In Figure 7 it is shown-applied to a base In which is designed to fit the new arm and furnace. The base It! is formed with a fiat top to provide a more compact structure, and the central shaft II is rotated by the spring motor 64. The sliding contact holder 28 is built into the casing ID at the upper corner thereof, and the sliding contact plate is actuated by a finger piece 65 working in a slot in the top of the casing and extending above the top of the casing. The other features of the casting apparatus are the same as in the other figures.

In Figure 5 a diagram of the electric circuits employed is illustrated. A pyrometer P is shown in circuit with thermocouple 25 through contacts 35 and 28 while an ammeter A, switch 66 and rheostat or other current controlling device 61 are included in the circuit to the heating coil 23 through contacts 35 and 21. Obviously, ad-

creasing the number of contacts.

In operation, the handle 51 is grasped and the bar l2 rotated to wind up the spring motor-in casing l0 or l0. The slidable contact plate 3| is then moved out into the path of contact block I 8 against the tension of the spring 32. The pressure of the spring motor forces contact block firmly against plate 3| and retains it in extended position. The circuits to the heating coil and thermocouple are connected through contacts 35, 26 and 21 in this position of plate 3|. The mold 45 is then clamped in position, metal is placed in the crucibleand the current turned on. When the desired temperature is reached, as determined by reference to the pyrometer, handle 51 is grasped and bar l2 moved to separate contact block l8 and sliding plate 31, whereupon spring 32' retracts plate 3|. Handle '51 is then released and bar l2 rotated at high speed by the spring motor in casing III or The molten metal in crucible 43 passes through sprue 44 into the mold 45 under the action of centrifugal force. By the use of thermocouple 25 and pyrometer P the desired temperature may be obtained before rotating arm l2, without relying upon visual inspection, and castings of a fine, uniform character may be obtained. The crucible 43 may be removed for cooling by opening door 40 and lifting out the crucible with a pair of tongs.

The flask holder 48 may be adjusted to clamp molds of various sizes while the counter weights may be adjusted to properly balance the bar 12. The inclined slot 49 insures a firm clamping of the mold. It will be seen that the bar l2 and contact holder 28 may be readily attached to the usual bases or may be included in a special base, as indicated in Figure '7. The plug 31 permits ready attachment to a control panel containing the switches and instruments shown in the diagram of Figure 5.

While I have shown and described the preferred embodiment of the invention, it is to be understood that various changes in the size, shape and arrangement of parts may be resorted to without departing from the spiritof the invention or the scope of the subjoined claims.

Having thus described my invention what I claim and desire to secure by Letters Patent is:

1. In a centrifugal casting machine, a base, a bar rotatably carried by said base, means to rotate said bar, a heating chamber carried by the bar, an electrical heating element in said chamber, a contact block depending from said bar and having contacts connected to said heating element, a sliding contact holder carried by said base, a sliding contact plate carried by said holder, contacts on said plate and connected to a source of electric current, and means to move the contact plate into the path of the contact block. A

2. In a centrifugal casting machine, a base, a bar rotatably carried by said base, means to ro-. tate said bar, a bracket secured to the bar and extending above and below the bar, a heating chamber carried by the bracket above the bar, an electrical heating element in the chamber, a contact block carried by the bracket below the bar and having contacts connected to said heating element, a sliding contact plate carried by the base, contacts on said plate connected to a source of electric current, means to move the sliding contact plate into the'path of the contact block to engage the contacts thereon and hold the bar against rotation, and resilient means to withdraw the contact plate and permit rotation of the bar when the contacts are disengaged.

having an electrical heating element, a contact block in fixed relation to said heating chamber, a stationary holder, a contact member mounted for movement in said holder from a retracted position out of engagement with said contact block to a projected position in which said contact member engages said block for respectively breaking and making the circuit through said heating element, and spring means for pressing said contact block against said contact member when the latter is in said projected position, said spring means being efiective to rotate said heating chamber when said contact member is in said retracted position thereof.

5. In a centrifugal casting machine comprising a heating chamber mounted for rotation, said heating chamber having an electrical heating element and a thermocouple therein, a contact block in fixed relation to said heating chamber and rotatable therewith, said heating element and said thermocouple each having a pair of terminal contact members carried by said block, a stationary holder, and a contact member mounted for movement in said holder from a retracted position out of engagement with said block to a projected position in which said contact member engages said terminal contact members and is in the path of rotation of said contactblock,

and spring actuated means for rotating said chamber when said contact member is in its retracted position and for pressing .said terminal contact members carried by said block' against said contact member when the latter is in said projected position thereof.

6. In a centrifugal casting machine, a base; a bar rotatably carried by said base, a bracket carried by said bar, said bracket comprising arms extending upwardly above said bar and arms extending downwardly below said bar, a heating chamber supported by said upwardly extending arms, said heating chamber having an electrical heating element, a contact block carried by said downwardly extending arms and having contacts connected to said heating element, and a movable contact member mounted on said base and movable into and out of the path of rotation of said contact block and into and out of engagement with said contacts of said contact block.

HERBERT R. BERGER. 

